Simply stated, a green roof is a roof on which vegetation takes the place of asphalt, gravel and shingles. A green roof consists of a waterproofing layer, a drainage layer, growing media (soil) and plants. Among the many benefits of a green roof are that it:

mitigates urban heat island

improves energy efficiency of building below by acting as shade and insulation

reduces and improves quality of stormwater runoff by retaining and filtering

restores lost wildlife habitat and native plants

creates aesthetic and recreational value on the roof

introduces produce growing opportunities (vertical farming)

increases life span of roofing membrane which offsets the initial cost to install

Engineering or retrofitting the water and wastewater system of a facility to reuse water to irrigate a green roof can provide these benefits plus substantially reduce potable water demands and costs. Austin is in the process of adopting codes and incentives for new building projects incorporating green roofs right now.